Coverity has spotted a possible problem with the OAS handling
(CID 1558464), where the error return of oas2bits() -1 is not
checked, which can cause an overflow in oas value.
oas2bits() is only called with valid inputs, harden the function
to assert that.
Reported-By: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20240722103531.2377348-1-smostafa@google.com
Link: https://lore.kernel.org/qemu-devel/CAFEAcA-H=n-3mHC+eL6YjfL1m+x+b+Fk3mkgZbN74WNxifFVow@mail.gmail.com/
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
SMMUv3 OAS is currently hardcoded in the code to 44 bits, for nested
configurations that can be a problem, as stage-2 might be shared with
the CPU which might have different PARANGE, and according to SMMU manual
ARM IHI 0070F.b:
6.3.6 SMMU_IDR5, OAS must match the system physical address size.
This patch doesn't change the SMMU OAS, but refactors the code to
make it easier to do that:
- Rely everywhere on IDR5 for reading OAS instead of using the
SMMU_IDR5_OAS macro, so, it is easier just to change IDR5 and
it propagages correctly.
- Add additional checks when OAS is greater than 48bits.
- Remove unused functions/macros: pa_range/MAX_PA.
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20240715084519.1189624-19-smostafa@google.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
The SMMUv3 spec (ARM IHI 0070 F.b - 7.3 Event records) defines the
class of events faults as:
CLASS: The class of the operation that caused the fault:
- 0b00: CD, CD fetch.
- 0b01: TTD, Stage 1 translation table fetch.
- 0b10: IN, Input address
However, this value was not set and left as 0 which means CD and not
IN (0b10).
Another problem was that stage-2 class is considered IN not TT for
EABT, according to the spec:
Translation of an IPA after successful stage 1 translation (or,
in stage 2-only configuration, an input IPA)
- S2 == 1 (stage 2), CLASS == IN (Input to stage)
This would change soon when nested translations are supported.
While at it, add an enum for class as it would be used for nesting.
However, at the moment stage-1 and stage-2 use the same class values,
except for EABT.
Fixes: 9bde7f0674 “hw/arm/smmuv3: Implement translate callback”
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20240715084519.1189624-4-smostafa@google.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
An access fault is raised when the Access Flag is not set in the
looked-up PTE and the AFFD field is not set in the corresponding context
descriptor. This was already implemented for stage 2. Implement it for
stage 1 as well.
Signed-off-by: Luc Michel <luc.michel@amd.com>
Reviewed-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Mostafa Saleh <smostafa@google.com>
Message-id: 20240213082211.3330400-1-luc.michel@amd.com
[PMM: tweaked comment text]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
hw/arm/smmuv3-internal.h uses the REG32() and FIELD()
macros defined in "hw/registerfields.h". Include it in
order to avoid when refactoring unrelated headers:
In file included from ../../hw/arm/smmuv3.c:34:
hw/arm/smmuv3-internal.h:36:28: error: expected identifier
REG32(IDR0, 0x0)
^
hw/arm/smmuv3-internal.h:37:5: error: expected function body after function declarator
FIELD(IDR0, S2P, 0 , 1)
^
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240118200643.29037-4-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Update the SMMUv3 ID register bit field definitions to the
set in the most recent specification (IHI0700 F.a).
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20230914145705.1648377-2-peter.maydell@linaro.org
The STE_CTXPTR() and STE_S2TTB() macros both extract two halves
of an address from fields in the STE and combine them into a
single value to return. The current code for this uses a GCC
statement expression. There are two problems with this:
(1) The type chosen for the variable in the statement expr
is 'unsigned long', which might not be 64 bits
(2) the name chosen for the variable causes -Wshadow warnings
because it's the same as a variable in use at the callsite:
In file included from ../../hw/arm/smmuv3.c:34:
../../hw/arm/smmuv3.c: In function ‘smmu_get_cd’:
../../hw/arm/smmuv3-internal.h:538:23: warning: declaration of ‘addr’ shadows a previous local [-Wshadow=compatible-local]
538 | unsigned long addr; \
| ^~~~
../../hw/arm/smmuv3.c:339:23: note: in expansion of macro ‘STE_CTXPTR’
339 | dma_addr_t addr = STE_CTXPTR(ste);
| ^~~~~~~~~~
../../hw/arm/smmuv3.c:339:16: note: shadowed declaration is here
339 | dma_addr_t addr = STE_CTXPTR(ste);
| ^~~~
Sidestep both of these problems by just using a single
expression rather than a statement expr.
For CMD_ADDR, we got the type of the variable right but still
run into -Wshadow problems:
In file included from ../../hw/arm/smmuv3.c:34:
../../hw/arm/smmuv3.c: In function ‘smmuv3_range_inval’:
../../hw/arm/smmuv3-internal.h:334:22: warning: declaration of ‘addr’ shadows a previous local [-Wshadow=compatible-local]
334 | uint64_t addr = high << 32 | (low << 12); \
| ^~~~
../../hw/arm/smmuv3.c:1104:28: note: in expansion of macro ‘CMD_ADDR’
1104 | dma_addr_t end, addr = CMD_ADDR(cmd);
| ^~~~~~~~
../../hw/arm/smmuv3.c:1104:21: note: shadowed declaration is here
1104 | dma_addr_t end, addr = CMD_ADDR(cmd);
| ^~~~
so convert it too.
CD_TTB has neither problem, but it is the only other macro in
the file that uses this pattern, so we convert it also for
consistency's sake.
We use extract64() rather than extract32() to avoid having
to explicitly cast the result to uint64_t.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-ID: <20230922152944.3583438-5-peter.maydell@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Parse stage-2 configuration from STE and populate it in SMMUS2Cfg.
Validity of field values are checked when possible.
Only AA64 tables are supported and Small Translation Tables (STT) are
not supported.
According to SMMUv3 UM(IHI0070E) "5.2 Stream Table Entry": All fields
with an S2 prefix (with the exception of S2VMID) are IGNORED when
stage-2 bypasses translation (Config[1] == 0).
Which means that VMID can be used(for TLB tagging) even if stage-2 is
bypassed, so we parse it unconditionally when S2P exists. Otherwise
it is set to -1.(only S1P)
As stall is not supported, if S2S is set the translation would abort.
For S2R, we reuse the same code used for stage-1 with flag
record_faults. However when nested translation is supported we would
need to separate stage-1 and stage-2 faults.
Fix wrong shift in STE_S2HD, STE_S2HA, STE_S2S.
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20230516203327.2051088-6-smostafa@google.com
[PMM: fixed format string]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
In preparation for adding stage-2 support.
Add IDR0 fields related to stage-2.
VMID16: 16-bit VMID supported.
S2P: Stage-2 translation supported.
They are described in 6.3.1 SMMU_IDR0.
No functional change intended.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Message-id: 20230516203327.2051088-2-smostafa@google.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
GBPA register can be used to globally abort all
transactions.
It is described in the SMMU manual in "6.3.14 SMMU_GBPA".
ABORT reset value is IMPLEMENTATION DEFINED, it is chosen to
be zero(Do not abort incoming transactions).
Other fields have default values of Use Incoming.
If UPDATE is not set, the write is ignored. This is the only permitted
behavior in SMMUv3.2 and later.(6.3.14.1 Update procedure)
As this patch adds a new state to the SMMU (GBPA), it is added
in a new subsection for forward migration compatibility.
GBPA is only migrated if its value is different from the reset value.
It does this to be backward migration compatible if SW didn't write
the register.
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20230214094009.2445653-1-smostafa@google.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
The Arm SMMUv3 includes an optional feature equivalent to the CPU
FEAT_BBM, which permits an OS to switch a range of memory between
"covered by a huge page" and "covered by a sequence of normal pages"
without having to engage in the traditional 'break-before-make'
dance. (This is particularly important for the SMMU, because devices
performing I/O through an SMMU are less likely to be able to cope with
the window in the sequence where an access results in a translation
fault.) The SMMU spec explicitly notes that one of the valid ways to
be a BBM level 2 compliant implementation is:
* if there are multiple entries in the TLB for an address,
choose one of them and use it, ignoring the others
Our SMMU TLB implementation (unlike our CPU TLB) does allow multiple
TLB entries for an address, because the translation table level is
part of the SMMUIOTLBKey, and so our IOTLB hashtable can include
entries for the same address where the leaf was at different levels
(i.e. both hugepage and normal page). Our TLB lookup implementation in
smmu_iotlb_lookup() will always find the entry with the lowest level
(i.e. it prefers the hugepage over the normal page) and ignore any
others. TLB invalidation correctly removes all TLB entries matching
the specified address or address range (unless the guest specifies the
leaf level explicitly, in which case it gets what it asked for). So we
can validly advertise support for BBML level 2.
Note that we still can't yet advertise ourselves as an SMMU v3.2,
because v3.2 requires support for the S2FWB feature, which we don't
yet implement.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20220426160422.2353158-4-peter.maydell@linaro.org
The Record bit in the Context Descriptor tells the SMMU to report fault
events to the event queue. Since we don't cache the Record bit at the
moment, access faults from a cached Context Descriptor are never
reported. Store the Record bit in the cached SMMUTransCfg.
Fixes: 9bde7f0674 ("hw/arm/smmuv3: Implement translate callback")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20220427111543.124620-1-jean-philippe@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
The bit to see if a CD is valid is the last bit of the first word of the CD.
Signed-off-by: Joe Komlodi <joe.komlodi@xilinx.com>
Message-id: 1626728232-134665-2-git-send-email-joe.komlodi@xilinx.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
They were introduced in commit 9bde7f0674 ("hw/arm/smmuv3: Implement
translate callback") but never actually used. Drop them.
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Acked-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20210325142702.790-1-yuzenghui@huawei.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Accroding to the SMMUv3 spec, the SPAN field of Level1 Stream Table
Descriptor is 5 bits([4:0]).
Fixes: 9bde7f0674f(hw/arm/smmuv3: Implement translate callback)
Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
Message-id: 20201124023711.1184-1-jiangkunkun@huawei.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Expose the RIL bit so that the guest driver uses range
invalidation. Although RIL is a 3.2 features, We let
the AIDR advertise SMMUv3.1 support as v3.x implementation
is allowed to implement features from v3.(x+1).
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20200728150815.11446-12-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
HAD is a mandatory features with SMMUv3.1 if S1P is set, which is
our case. Other 3.1 mandatory features come with S2P which we don't
have.
So let's support HAD and advertise SMMUv3.1 support in AIDR.
HAD support allows the CD to disable hierarchical attributes, ie.
if the HAD0/1 bit is set, the APTable field of table descriptors
walked through TTB0/1 is ignored.
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20200728150815.11446-11-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Add the support for AIDR register. It currently advertises
SMMU V3.0 spec.
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20200728150815.11446-10-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
The SMMU IIDR register is at 0x018 offset.
Fixes: 10a83cb988 ("hw/arm/smmuv3: Skeleton")
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20200728150815.11446-9-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Enhance the smmu_iotlb_inv_iova() helper with range invalidation.
This uses the new fields passed in the NH_VA and NH_VAA commands:
the size of the range, the level and the granule.
As NH_VA and NH_VAA both use those fields, their decoding and
handling is factorized in a new smmuv3_s1_range_inval() helper.
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20200728150815.11446-8-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
The bit offsets in the EVT_SET_ADDR2 macro do not match those specified
in the ARM SMMUv3 Architecture Specification. In all events that use
this macro, e.g. F_WALK_EABT, the faulting fetch address or IPA actually
occupies the 32-bit words 6 and 7 in the event record contiguously, with
the upper and lower unused bits clear due to alignment or maximum
supported address bits. How many bits are clear depends on the
individual event type.
Update the macro to write to the correct words in the event record so
that guest drivers can obtain accurate address information on events.
ref. ARM IHI 0070C, sections 7.3.12 through 7.3.16.
Signed-off-by: Simon Veith <sveith@amazon.de>
Acked-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Message-id: 1576509312-13083-6-git-send-email-sveith@amazon.de
Cc: Eric Auger <eric.auger@redhat.com>
Cc: qemu-devel@nongnu.org
Cc: qemu-arm@nongnu.org
Acked-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
There are two issues with the current value of SMMU_BASE_ADDR_MASK:
- At the lower end, we are clearing bits [4:0]. Per the SMMUv3 spec,
we should also be treating bit 5 as zero in the base address.
- At the upper end, we are clearing bits [63:48]. Per the SMMUv3 spec,
only bits [63:52] must be explicitly treated as zero.
Update the SMMU_BASE_ADDR_MASK value to mask out bits [63:52] and [5:0].
ref. ARM IHI 0070C, section 6.3.23.
Signed-off-by: Simon Veith <sveith@amazon.de>
Acked-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Message-id: 1576509312-13083-3-git-send-email-sveith@amazon.de
Cc: Eric Auger <eric.auger@redhat.com>
Cc: qemu-devel@nongnu.org
Cc: qemu-arm@nongnu.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
An IOVA/ASID invalidation is notified to all IOMMU Memory Regions
through smmuv3_inv_notifiers_iova/smmuv3_notify_iova.
When the notification occurs it is possible that some of the
PCIe devices associated to the notified regions do not have a
valid stream table entry. In that case we output a LOG_GUEST_ERROR
message, for example:
invalid sid=<SID> (L1STD span=0)
"smmuv3_notify_iova error decoding the configuration for iommu mr=<MR>
This is unfortunate as the user gets the impression that there
are some translation decoding errors whereas there are not.
This patch adds a new field in SMMUEventInfo that tells whether
the detection of an invalid STE must lead to an error report.
invalid_ste_allowed is set before doing the invalidations and
kept unset on actual translation.
The other configuration decoding error messages are kept since if the
STE is valid then the rest of the config must be correct.
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20190822172350.12008-6-eric.auger@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Header guard symbols should match their file name to make guard
collisions less likely.
Cleaned up with scripts/clean-header-guards.pl, followed by some
renaming of new guard symbols picked by the script to better ones.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190315145123.28030-6-armbru@redhat.com>
[Rebase to master: update include/hw/net/ne2000-isa.h]
The event queue management is broken today. Event records
are not properly written as EVT_SET_* macro was not updating
the actual event record. Also the event queue interrupt
is not correctly triggered.
Fixes: bb981004ea ("hw/arm/smmuv3: Event queue recording helper")
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20180921070138.10114-3-eric.auger@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
In case the STE's config is "Bypass" we currently don't set the
IOMMUTLBEntry perm flags and the access does not succeed. Also
if the config is 0b0xx (Aborted/Reserved), decode_ste and
smmuv3_decode_config currently returns -EINVAL and we don't enter
the expected code path: we record an event whereas we should not.
This patch fixes those bugs and simplifies the error handling.
decode_ste and smmuv3_decode_config now return 0 if aborted or
bypassed config was found. Only bad config info produces negative
error values. In smmuv3_translate we more clearly differentiate
errors, bypass/smmu disabled, aborted and success cases. Also
trace points are differentiated.
Fixes: 9bde7f0674 ("hw/arm/smmuv3: Implement translate callback")
Reported-by: jia.he@hxt-semitech.com
Signed-off-by: jia.he@hxt-semitech.com
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1529653501-15358-2-git-send-email-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This patch implements the IOMMU Memory Region translate()
callback. Most of the code relates to the translation
configuration decoding and check (STE, CD).
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Prem Mallappa <prem.mallappa@broadcom.com>
Message-id: 1524665762-31355-10-git-send-email-eric.auger@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Let's introduce a helper function aiming at recording an
event in the event queue.
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1524665762-31355-9-git-send-email-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Now we have relevant helpers for queue and irq
management, let's implement MMIO write operations.
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Prem Mallappa <prem.mallappa@broadcom.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1524665762-31355-8-git-send-email-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
We introduce helpers to read/write into the command and event
circular queues.
smmuv3_write_eventq and smmuv3_cmq_consume will become static
in subsequent patches.
Invalidation commands are not yet dealt with. We do not cache
data that need to be invalidated. This will change with vhost
integration.
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Prem Mallappa <prem.mallappa@broadcom.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1524665762-31355-7-git-send-email-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
We introduce some helpers to handle wired IRQs and especially
GERROR interrupt. SMMU writes GERROR register on GERROR event
and SW acks GERROR interrupts by setting GERRORn.
The Wired interrupts are edge sensitive hence the pulse usage.
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Prem Mallappa <prem.mallappa@broadcom.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1524665762-31355-6-git-send-email-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This patch implements a skeleton for the smmuv3 device.
Datatypes and register definitions are introduced. The MMIO
region, the interrupts and the queue are initialized.
Only the MMIO read operation is implemented here.
Signed-off-by: Prem Mallappa <prem.mallappa@broadcom.com>
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1524665762-31355-5-git-send-email-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
